Pressor response to vasopressin and impaired baroreflex function in DOC-salt hypertension

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Abstract
Baroreflexes and pressor responses to i.v. arginine vasopressin (AVP) and phenylephrine (PE) were evaluated in conscious, less severely hypertensive deoxycorticosterone (DOC)-salt-treated rats, hypertensive DOC-salt-treated rats, and control rats (n = 6, each group). Pressor responses were retested after ganglionic blockade with chlorisondamine chloride. In control rats pressor responses to AVP were augmented more than those to PE after ganglion blockade; thus AVP appeared uniquely to augment baroreflex buffering. In hypertensive DOC-salt-treated rats baroreflexes were impaired (P < 0.05); pressor responsiveness to AVP was augmented compared with control rats (P < 0.05). After ganglion blockade augmentation of pressor responses was similar for AVP and PE. In less severely hypertensive rats baroreflexes were normal; pressor responses to AVP and PE were like those in control rats before and after ganglion blockade. Apparently AVP augments baroreflex buffering, which imposes a restraint on pressor effects of AVP that is not evident with PE. In hypertensive DOC-salt-treated rats a defect in baroreflex buffering during infusion of AVP may contribute to augmented pressor effects of AVP.